1. Field of the Invention
This invention relates to a continuous fermenter vessel for receiving an agitated suspension culture of cells.
2. Description of the Related Art
Recent advances in the commercialisation of products produced by the in vitro fermentation of cells have led to a growing interest in the design of improved fermenter vessels and fermentation processes.
Fermentation is usually carried out either in a batch process or in a continuous process. Continuous processes are advantageous since they enhance the productivity of a given fermenter and reduce the nonproductive downtime necessary for cleaning and sterilisation which is normally required in a batch fermenter.
In known continuous fermenter vessels, a suspension of cells in an appropriate culture medium is agitated and maintained at a suitable temperature for fermentation. Suspension culture is continuously withdrawn from the fermenter, balanced by a continuous supply of fresh culture medium. A significant disadvantage of such fermenters is the continual loss of cells caused by the removal of culture. Fermenters are known in which removed suspension culture is passed through a continuous centrifugal separation device which separates cells from the culture supernatant. The cells are then fed back into the suspension culture.
In another known fermenter, a rotating basket of a filter material is provided, partially submerged in the culture, such that the inside of the basket is separated from the suspension culture by the filter. Culture supernatant passes through the filter and may be withdrawn continuously, whilst cells remain in the suspension culture. The rotation of the basket in the suspension culture reduces clogging of the filter material.
These known devices for providing cell feedback in continuous suspension cultures are complicated mechanically, require energy for their operation and may cause detrimental effects, such as cell rupture, upon the suspension culture. These features combine to reduce the economic viability of fermentation processes based on such fermenters.